import java.util.LinkedList;
import java.util.Queue;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: yang
 * Date: 2022-07-11
 * Time: 16:40
 */
public class BinaryTree {
    TreeNode root;
    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public void createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');

        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
        this.root = A;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null)return;
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null)return;
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null)return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }


    int size(TreeNode root) {
        if(root == null)return 0;
        return 1 + size(root.left) + size(root.right);
    }


    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount(TreeNode root) {
        if(root == null)return 0;
        if(root.left == null && root.right == null)return 1;
        return getLeafNodeCount(root.left) + getLeafNodeCount(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(k == 1)return 1;
        return getKLevelNodeCount(root.left,k-1) + getKLevelNodeCount(root.right,k-1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if(root == null)return 0;
        return 1 + Math.max(getHeight(root.left),getHeight(root.right));
    }


    // 检测值为value的元素是否存在
    Boolean find(TreeNode root, char val) {
        if(root == null)return false;
        if(root.val == val)return true;
        return false || find(root.left,val) || find(root.right,val);
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        Queue<TreeNode> q = new LinkedList<>();
        if(root == null)return;
        q.offer(root);
        while(!q.isEmpty()){
            int size = q.size();
            for (int i = 0; i < size; i++) {
                TreeNode node = q.poll();
                System.out.print(node.val + " ");
                if(node.left != null)q.offer(node.left);
                if(node.right != null)q.offer(node.right);
            }
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        return true;
    }

    public static void main(String[] args) {
        BinaryTree tree = new BinaryTree();
        tree.createTree();
        System.out.println(tree.size(tree.root));
        System.out.println(tree.getLeafNodeCount(tree.root));
        System.out.println(tree.getKLevelNodeCount(tree.root,3));
        System.out.println(tree.getHeight(tree.root));
        System.out.println(tree.find(tree.root,'H'));
        tree.preOrder(tree.root);
        System.out.println();
        tree.inOrder(tree.root);
        System.out.println();
        tree.postOrder(tree.root);
        System.out.println();
        tree.levelOrder(tree.root);
        System.out.println();
    }
}